Three powerhouse tech firms reported quarterly earnings after the bell Tuesday: Apple (AAPL - Analyst Report), Microsoft (MSFT - Analyst Report) and Yahoo (YHOO -Analyst Report). All three had fair-to-good results, but late-market trading took down share prices for each firm.

Apple posted another impressive quarter with $1.85 per share on $49.6 billion in sales in fiscal Q3 2015, a beat on both top and bottom lines -- the Zacks consensus estimates were $1.80 per share and $49.5 billion in revenues. Apple sold 47.5 million iPhone sales in the quarter, 10.9 million iPads and a better-than-expected 4.8 million Macs. Gross margins topped expectations at 39.7 percent, and Apple CEO Tim Cook said the Apple Watch was "exceeding expectations." So why are AAPL shares down 7.6 percent in late trading?

In a word: guidance. Both gross margin and September quarter expectations are flat with projections for the Q3 numbers just reported. Also, as is often the case when a run-up prior to an earnings announcement occurs -- and Apple was up 6 percent over the past 5 days before the after-market sell-off -- investors tend to "sell the news." There was also no word (prior to the conference call) on Apple TV or Apple music -- two segments investors were perhaps looking for to provide growth numbers looking forward.

In any case, Apple is still performing quite well in its core businesses on first blush. According to Cook, only 27 percent of iPhone users have yet moved up to the 6 or 6+ models, while switches from Android users to iOS is reportedly the highest they have ever been.

Microsoft's Q4 posted a beat on both top and bottom lines after the bell. The software giant reported earnings of 62 cents per share (a 10.7 percent positive surprise, which is higher than the trailing 4-quarter average beat of 9.6 percent) on $22.18 billion. It's commercial cloud revenue grew 88 percent year over year (to an annualized run rate of greater than $8 billion per year), which is no doubt supplementing the falling PC market, which Microsoft is actively migrating out of.

And CEO Satya Nadella cited Surface, Bing, Office 365, and others as demonstrating "at least double-digit growth." Yet Microsoft shares have dipped 3.8 percent in after-market trading, effectively surrendering the 3.31 percent gains MSFT had enjoyed over the past 5 days alone. Is this also a "sell the news" scenario, or are there some subtler issues regarding cloud migration and/or PC business disappointment that will only be addressed in the upcoming conference call?

Finally, Yahoo has reported its first negative earnings surprise in the past 4 quarters, with 3 cents per share (accounting for stock-based compensation and other non-recurring items) and $1.04 billion is revenues, which amounted to a modest beat on the top line. Yet YHOO shares are also down in late trading, basically on guidance for fiscal Q3 (September) between $1-1.04 billion, down from the $1.06 billion in the Zacks consensus estimate. Between a possible change in the IRS ruling on Yahoo's planned spinoff of Alibaba (BABA - Analyst Report) and the fact that 79 percent of Yahoo's business is still PC-related, it's easier to see how shares have tumbled over 22 percent, year to date.